Determination of trace nitrites and nitrates in human urine and plasma by field-amplified sample stacking open-tubular capillary electrochromatography in a nano-latex coated capillary

Abstract

The associations of nitric oxide (NO) with many diseases are still being discovered, and sometimes, NO levels in the body fluids are too low to be detected. Thus, the determination methods for trace nitrites and nitrates in urine and plasma of healthy volunteers and rheumatoid arthritis (RA) patients are necessary. Using trimethylamine aminated polychloromethyl styrene nano-latex coated capillary column (ccc-TMAPL) and field-amplified sample stacking (FASS) injection, the sensitive open-tubular capillary electrochromatography (OT-CEC) methods for determining trace nitrites and nitrates in urine and plasma of healthy volunteers and RA patients were set up. The limits of detection for both nitrite and nitrate were 1 ng/mL. The intra- and inter-day relative standard deviations (RSDs) of the methods were less than 1.9%, and recoveries were between 89 and 96%. Plasma nitrate (diluted 10 times) levels were 93–301 ng/mL for healthy volunteers and 222–421 ng/mL for RA patients, respectively. Meanwhile, plasma nitrite levels were 7–18 and 40–82 ng/mL, respectively. The urinary nitrite levels were significantly elevated in RA patients. The proposed sensitive FASS-OT-CEC methods for trace nitrites and nitrates hold the promise of practical applications in a wide array of biological analyses, clinical and pathophysiology studies of the diseases related with NO hyperproduction and metabolites.